土石混合体渗透性现场试坑试验研究

针对唐钢司家营铁矿Ⅲ采场露天转井下开采回填废石设计研究工程要求,在该矿区Ⅲ采场附近进行了大尺度现场渗透试验。开挖3个大尺寸试坑,在各试坑中分层回填不同粒径范围及厚度的废石(土)进行试坑注水试验;测定回填土石混合体的近似渗透系数,测试土石混合体的粒径组成,并计算出各坑土石混合体的平均粒径和非均匀度。试验研究发现,回填土石混合体的渗透系数分别随平均粒径与非均匀度的增大而增大。降低回填废石(土)的平均粒径和非均匀度可以有效降低回填废石层的渗透性。

苏北围垦大堤堤基土渗透破坏现场试验研究

在分析江苏苏北淤积海岸带淤积土结构特性与粒组组成的基础上,采用数码摄像与成像跟踪渗透全过程的现场渗透变形试验与室内颗分试验,通过现场试坑模拟高潮位及不同潮位变动频率条件下堤基渗透破坏形式与临界破坏动力条件,观测土体在不同水位变化条件下发生渗透破坏的细观特征,进一步研究了颗粒移动规律、渗透破坏类型与水力梯度、流量的关系,总结出围垦大堤堤基土渗透破坏的规律。研究表明,堤基土颗粒分布特征、颗粒级配对渗透变形的类型具有决定性作用的结论。为控制土体渗透变形稳定性的改善土体不均匀系数的措施提供重要试验依据。

土石混合体渗透性能的试坑双环注水试验研究

针对西南地区某大型水电站近坝段内一土石混合体构成的滑坡,利用改进的双环注水试验设备进行了现场渗透试验。试验中在滑体和滑带的不同部位分别布置了4个试验点和6个试验点。试验结果表明:土石混合体的渗透系数较大,接近无黏性粗粒土的渗透系数,并且滑体处平均渗透系数是滑带处的3～4倍。结合室内颗粒分析试验对滑体和滑带土进行的分析表明,低于5 mm粒径的细颗粒含量、密度、颗粒形状及物质来源等因素导致两者渗透系数差异的主要原因。

钱塘江古海塘塘基防渗加固现场试验研究

目前仍然坚守在防洪御潮第一线的钱塘江明清古海塘,由于年代久远,部分塘段的塘趾部位存在流土现象,因此,选用合理且不破坏古海塘风貌的塘基防渗加固方案来保护古海塘十分必要。以浙江海宁某明清古海塘试验段为依托,通过现场试验,对比研究了4种塘基防渗加固保护方案,通过有限元分析、现场渗透试验、加固后开挖检验、施工期对古海塘的影响监测等手段,分析总结了各加固方案的优缺点,得到了机械适当改制后的"塘趾旋喷注浆"方案为优选方案的结论,研究成果对下一步钱塘江临江古海塘保护工程的塘基防渗加固方案选取具有重要参考价值。

土石坝防渗心墙料渗透系数测试方法对比研究

渗透系数是土石坝防渗心墙料填筑质量评价的重要指标之一。针对云南省内多个土石坝工程,对施工碾压后的防渗心墙料,采用现场双环、单环法和室内变水头法进行了渗透试验,并采用规范推荐的渗透系数近似值与较精确值方法计算了两种原位测试方法的心墙料渗透系数,并与变水头方法计算的渗透系数进行了对比分析。结果表明,采用近似值计算渗透系数偏差较大,建议在实际工程质量检测中采用精确值计算法;单环法和双环法的试验结果较为接近,可以利用单环法代替双环法进行防渗心墙料的现场渗透测试,这种替代能够加速现场渗透系数的检测效率,提高施工速度。最后研究了不同饱和时间对渗透系数测定的影响。

土石坝坝壳料渗透系数测试方法研究

土石坝填筑后的渗透特性是评价施工质量的重要指标。针对云南省内5个新建的土石坝工程的坝壳料，采用试坑单环注水、试坑直接注水和室内粗粒土常水头渗透方法进行坝壳料的渗透系数测定，将三种测试方法获得的渗透系数进行了对比。研究表明，试坑直接注水法适用于适用于渗透系数较大的坝壳料（1×10-1～1×10-3 cm/s），试坑单环注水法适用于渗透系数稍小的土料（＜1×10-2 cm/s），而室内常水头法适用于各类坝壳料的渗透材料；需要根据情况采取合理的测试方法测定不同坝壳料的渗透性。试坑直接注水法所测渗透系数与试坑单环注水法的结果较为接近，测试结果能反映坝壳料碾压后的渗流过程，测试速度快，仪器安装简便，在工期较为紧迫的条件下，可以采用试坑直接注水法代替单环法进行坝壳料渗透系数的现场测定。

深层搅拌粧在新加坡滨海南地铁站中的应用

I新加坡滨海南地铁站区域的地层中包含海相黏土。在施工中,采用深层搅拌桩对海相黏土进行处理,以满足工程要求。通过无侧限抗压强度试验、现场渗透试验获得试验桩的不排水抗剪强度、弹性模量、渗透系数,以验证所提出的配比能否满足设计要求。根据现场实践经验,提出了施工过程中应当注意的事项。

Theory and test research on permeability of coal and rock body influenced by mining

Stress distribution rules and deformation and failure properties of coal and rockbodies influenced by mining were analyzed.Experimental research on permeability of coaland rock samples under different loading conditions was finished in the laboratory.In-situmeasurement of coal permeability influenced by actual mining was done as well.Theoryanalysis show that permeability varied with damage development of coal and rock understress,and the influence of fissure on permeability was greatest.Laboratory results showthat under different loading conditions permeability was different and it varied with stress,which indicated that permeability was directly related to the loading process.In-situ testsshowed that permeability is related to abutment stress to some degree.The above resultsmay be referenced to gas prevention and drainage.

Simultaneous hydraulic fracturing of ultra-low permeability sandstone reservoirs in China: Mechanism and its field test

Based on the impact of the stress perturbation effect created by simultaneous propagation of multiple fractures in the process of simultaneous hydraulic fracturing, a thorough research on the mechanism and adaptation of simultaneous fracturing of double horizontal wells in ultra-low permeability sandstone reservoirs was conducted by taking two adjacent horizontal wells(well Yangping-1 and well Yangping-2 located in Longdong area of China Changqing Oilfield) as field test wells. And simultaneous fracturing optimal design of two adjacent horizontal wells was finished and employed in field test. Micro-seismic monitoring analysis of fracture propagation during the stimulation treatment shows that hydraulic fractures present a pattern of complicated network expansion, and the well test data after fracturing show that the daily production of well Yangping-1 and well Yangping-2 reach105.8 t/d and 87.6 t/d, which are approximately 9.4 times and 7.8 times the daily production of a fractured vertical well in the same area, respectively. Field test reflects that simultaneous hydraulic fracturing of two adjacent horizontal wells can enlarge the expansion area of hydraulic fractures to obtain a lager drainage area and realize the full stimulation of ultra-low permeability sandstone reservoirs in China Changqing oilfield. Therefore, simultaneous fracturing of two adjacent horizontal wells provides a good opportunity in stimulation techniques for the efficient development of ultra-low permeability reservoirs in China Changqing oilfield,and it has great popularization value and can provide a new avenue for the application of stimulation techniques in ultra-low permeability reservoirs in China.

岩土工程注浆施工前的现场原位调查

在松散土层或含水岩层裂隙中采取注浆工法能够固结土颗粒或充塞岩层裂隙以获得土(岩)层力学性质改善而满足设计要求的土层加固,是岩土工程施工的一项重要工作。注浆施工前的现场调查、试验、设计及施工及注浆效果确认是注浆工法的五个重要的环节;施工前对现场充分调查及对调查结果的准确分析研讨对能够保障注浆施工的合理有效,同时对降低事故发生率及事故处理所花费的大量时间和费用至关重要。